Gas-shielded metal-arc welding



United States Patent GAS-SHIELDED METAL-ARC WELDING Donald M. Yenni, Williamsville, and Kenneth L. Thomas,

Kenmore, N. Y., assignors to Union Carbide and Carbon Corporation, a corporation of New York No Drawing. Application January 5, 1954, Serial No. 402,406

6 Claims. (Cl. 219-) This invention relates to gas-shielded metal-arc welding and, more particularly, to such arc welding with relatively high-current density like that proposed by Muller et al. No. 2,504,868 and Kennedy 2,532,410.

Generally, in shielded-inert-gas-metal-arc or sigma welding, the gas is argon or helium. Recently, as disclosed in the application of R. T. Breymeier, Serial No. 210,397, filed February 10, 1951, in sigma welding carbon steel, however, it has been found beneficial to use argon containing some oxygen such as 110% in sigma welding. Also, it has been proposed in Patent No. 2,591,926 to use a mixture of helium and argon as the shielding gas for non-consumable or refractory metal electrode arc welding in which the electrode is tungsten or thoriated tungsten. But it is impossible to predict beforehand that such proposal for that kind of arc welding would be suitable also for sigma welding.

In an investigation of various shielding gases and gas mixtures for sigma welding rimmed, killed or semi-killed carbon steel, we have discovered that wholly unexpected improvements are obtained with a shielding gas consisting of a mixture of helium, argon and carbon dioxide. For example, an arc shielding gas composed of a mixture of 80% helium, argon and 5% carbon dioxide produces a quiet, spatter-free arc, resulting in a satisfactory weld bead deposit. We have established that for sigma welding carbon steel, the most suitable shielding gas is one composed of 40-80% helium, 3-5 carbon dioxide and the balance argon. Satisfactory results are obtainable, however, when the shielding gas consists of 310 carbon dioxide, 40-80% helium and the balance argon for sigma welding carbon steel with direct current reverse polarity (DCRP). The carbon dioxide has a stabilizing influence on are performance when used with a mixture of helium and argon in concentrations not exceeding 10% CO2.

Most of the following performance data were secured in igma welding single pass beads on one-quarter inch thick carbon steel plate with an electrode, which is sold by the Linde Air Products Company as No. 32 CMS, of one-sixteenth inch diameter. No. 32 CMS welding wire .contains about 0.12% carbon, 1.0-1.2% manganese, 0.25% silicon, 0.35% chromium, not more than 0.015% sulphur and the balance iron. Data are given below for sigma welding runs using various helium-argon-carbon dioxide mixtures containing 1, 3, 5 and 10% carbon dioxide.

Beads were made at and 50 ipm with direct currentreverse polarity and at 25 ipm With direct current-straight polarity power. A welding speed of 25 ipm was selected since this represents the maximum speed for producing acceptable welds on 4-inch thick steel plate with pure argon and is also about the maximum speed for hand welding methods. Although arc current was substantially constant for a given welding speed and polarity, some changes will be noticed in arc operating voltage. The voltage for most satisfactory operation with each shielding gas mixture was selected.

The test beads were intended to have penetration somewhat greater than half the plate thickness or 0.125 inch, and a bead width-to-height ratio of four or more. A desirable dilution is or greater. Dilution is the ratio of melted base metal area to total melted area on the bead cross-section. These conditions apply to double pass, square butt welding.

TABLE I Sigma welding with helium, argon, CO2 mixtures 0n inch mild steel (Part I DORP-25 I. P. M.

Shielding Weld- Gas Power Filler Spat- Run Rod ter Ht. Penet.

Speed He A 002 Amp. Volts DORP-50I P M 57 3 450 28 390 Mi1d 095 .170 37 3 440 30 360 do 070 .160 27 3 440 30 360 (lo .075 .170 55 5 440 30 360 (lo .080 .170 35 5 440 30 360 do .075 .180 25 5 440 30 360 .do 075 .160 50 10 440 30 350 do .070 .170 30 10 440 30 350 do .090 .180 20 10 440 30 360 .do.. .080 .170

DOSP25 I P. M.

55 5 350 28 340 Bad..- .165 .060 25 5 350 28 375 t1o .125 .070 50 10 350 28 325 .do .095 .080 20 10 330 30 365 do .140 .055

(ParZII) DCRP-25 I. P. M.

Run Width W/H Area Dilu- Bead Defects tion .655 10. 1 .061 57 Ropey. .705 11.7 .080 69 Irregularpinh0le porosity. 635 9. 8 .072 63 Do. 565 8. 1 .065 58 N onesmooth, regular. .600 8. 6 072 57 Do. .545 7. 8 .061 61 D0. 490 6. 1 059 56 Do. .540 7. 7 .069 57 Do. .560 7.0 .071 58 D0. .590 8. 4 .069 57 D0. .435 5. l 072 58 Peaked. .490 5. 2 .077 61 Do. .540 5. 7 .073 59 Do.

I CRP-50 I. P. M.

86 .350 3. 7 .059 54 Smooth high.

8 .370 5v 3 .053 63 Slight}:1 undercut-smooth 1g 380 5. 1 057 62 None-excellent. .390 4. 9 .056 61 N one-fairly smooth. .380 5. l .057 63 None-good. 365 4. 0 053 59 None-excellent. .375 5. 3 .057 62 Sligl1t-CLP -excellent. .350 3.9 .061 63 SlightOLP and undercut O. K. otherwise. 95 .365 4.6 .057 63 SlightOLP and slight undercut.

I GLP is center line porosity.

DCSP25 I. P. M.

82 .450 2. 7 .064 34 Irregular, very high peak. 81 495 3.9 .075 36 None-high peak.

79 .495 5. 2 .070 50 Nonetoo shallow.

80 540 i 3. 9 073 32 Too high.

Note-All weld heads made on 34 inch OR steel, using l-ta inch diameter No. 32 OMS rod.

Total gas flow: 100 c. I. h.

Performance with various argon-helium ratios and carbon dioxide concentrations of 1, 3, and 10% are shown in Table I above. Acceptable weld beads were made at 50 ipm using 3% CO2 (run 89), 5% CO2 (run 90), and except for slight center line porosity, using 10% CO2. It is noted that weld bead quality improves with increasing helium content up to 70%, and that 80% (run 75) the bead is excellent though spatter is becoming noticeable. Therefore, a recommended mixture for DCRP welding of mild steel would be 70% helium, 25% argon, 5% CO2.

Dilution and bead width-to-height ratio show that most of these welds have satisfactory cross-sections. Arc operation with such mixtures is remarkably stable and little spatter is experienced. Thus, the addition of carbon dioxide to helium-argon mixture increases are stability and reduces spatter. Smoothness of weld surface and are stability are considerably better than that of comparable beads made with oxygen-argon. The increased arc stability and smoothness of operation make the use of helium-argon-oxygen mixtures ideal for hand sigma welding operations.

According to our invention the best shielding gas compositions for use under established sigma welding conditions should contain 3 to 5% carbon dioxide, from 40 to 70% helium and the remainder argon.

The invention obviously is suitable for sigma welding other metals such as stainless steels, as well as carbon steels.

We claim:

1. A shielding gas for direct current reverse polarity sigma welding carbon steel, composed of a mixture containing 3-10% carbon dioxide, -80% helium, and 10-57% argon.

2. A shielding gas composition for direct current reverse polarity sigma welding of carbon steel, consisting of helium, 25% argon, and 5% carbon dioxide.

3. A shielding gas for direct current reverse polarity sigma welding carbon steel which is composed of a mixture of carbon dioxide, helium and argon, containing 40- helium, 3-5% carbon dioxide, and 15-57% argon.

4. Process of gas-shielded metal-arc welding which comprises striking direct current reverse polarity arc between the work and a fusible metal electrode, feeding such electrode toward such work as molten metal is transferred therefrom to the work through such arc, and shielding the arc and adjacent metal with a gas stream consisting of a mixture containing 40-80% commercially pure helium, 3-5% commercially pure carbon dioxide and 15-57% commercially pure argon.

5. Process as defined by claim 4, in which the work and electrode are composed of carbon steel.

6. Process as defined by claim 4, in which the work and electrode are composed of stainless steel.

References Cited in the file of this patent UNITED STATES PATENTS 1,519,007 Paterson Dec. 9, 1924 2,504,867 Muller Aug. 10, 1950 2,504,868 Muller Aug. 10, 1950 2,544,711 Mikhalapov Mar. 13, 1951 2,576,793 Jordan Nov. 27, 1951 2,591,926 Gibson Apr. 8, 1952 OTHER REFERENCES Arc Welding in Controlled Atmospheres, by Doan and Smith, pp. 1108-1165 in March 1940, Welding Research Supplement, 

1. A SHIELDING GAS FOR DIRECT CURRENT REVERSE POLARITY SIGMA WELDING CARBON STEEL, COMPOSED OF A MIXTURE CONTAINING 3-10% CARBON DIOXIDE, 40-80% HELIUM, AND 10-57% ARGON. 